The nature of the emission transition of the octahedral uranate group

Abstract

Decay times of the green luminescence of U6+ in oxides with perovskite structure are reported. The influence of the site symmetry is found to be considerable. The temperature dependence of the decay time gives evidence for a coupling of the electronic transition with a phonon of about 200 cm−1 in the excited state. The results show the emission to originate from a parity-forbidden transition, vibronically allowed by coupling with vibrations of ungerade symmetry.